SVT 40 Fail to Fire

haretrigger

haretrigger

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Lower Mainland, BC
I recently made a range trip with my new to me Tokarev SVT 40. This is not the first one I have owned so I am familiar with adjusting the gas setting, cleaning and degreasing the regulator and piston etc. I also throughly cleaned the chamber and the bolt.

I experienced numerous FTF's with Czech surplus 7.62x54r from the get go, and I am wondering if anyone else has had a similar experience and what the cause of this rifles issue might be? I am pretty sure that the ammo is not the source of the problem as it is out of a recently opened crate that has shot well out of another Tokarev. My Mosin M38 also loves to devour the same ammo without a hitch, but I realize that's like comparing apples and oranges in terms of the force that the firing pin spring strikes the primers with!

Basically, I'm wondering what I should be looking at first before I simply start changing every miscellaneous part that I can think of!
 
haretrigger said:
I recently made a range trip with my new to me Tokarev SVT 40. This is not the first one I have owned so I am familiar with adjusting the gas setting, cleaning and degreasing the regulator and piston etc. I also throughly cleaned the chamber and the bolt.

I experienced numerous FTF's with Czech surplus 7.62x54r from the get go, and I am wondering if anyone else has had a similar experience and what the cause of this rifles issue might be? I am pretty sure that the ammo is not the source of the problem as it is out of a recently opened crate that has shot well out of another Tokarev. My Mosin M38 also loves to devour the same ammo without a hitch, but I realize that's like comparing apples and oranges in terms of the force that the firing pin spring strikes the primers with!

Basically, I'm wondering what I should be looking at first before I simply start changing every miscellaneous part that I can think of!
Click to expand...
Did the firing pin make some mark on the primer? Could be a worn firing pin or a weak hammer spring.
Jocelyn
 
Thanks for the reply Jocelyn. Yes the primer is indented. I actually just pulled the bolt apart and looked at the firing pin very closely. I think the problem was caused by a hairline crack towards the rear of the pin. The crack starts towards the rear of the notch and the pin appears slightly bent. This seems to impose some friction on the pin which is perhaps causing the light strikes?
I'll try to get some pics up in a bit, but first I'm going to see if I might happen to have a spare firing pin in my parts box. Pretty sure I bought one a while back, at least I can compare that way.
 
Sounds mechanical related. A bit off the topic or not, I'm not impressed with the Czech 7.72x54r surplus ammo. I have a partial crate that has ftf in my Mosins as well as my SVT40. It was a 73 vintage if I recall. Substantially more duds than any other surplus ammo I've had.
 
haretrigger said:
Thanks for the reply Jocelyn. Yes the primer is indented. I actually just pulled the bolt apart and looked at the firing pin very closely. I think the problem was caused by a hairline crack towards the rear of the pin. The crack starts towards the rear of the notch and the pin appears slightly bent. This seems to impose some friction on the pin which is perhaps causing the light strikes?
I'll try to get some pics up in a bit, but first I'm going to see if I might happen to have a spare firing pin in my parts box. Pretty sure I bought one a while back, at least I can compare that way.
Click to expand...
With the bolt removed, you should be able to push on the firing pin at the rear with a finger to see if move easily.
Jocelyn
 
Just to update:
Sourced a used firing pin from Epps, and installed it - Not one fail to fire yet in 250 rounds of surplus!

What would cause a firing pin to crack? Dry firing? Excessive use?
 
Dry firing is a LOT harder on firing pins than people would like to think. When you're firing ammunition, at least the pin has something to cushion its headlong rush: the primer. No primer, the pin runs forward very fast and brings up solid inside the bolt but with a shock: steel on steel.

AG42/B has the same problem, compounded by the fact that the pins are small enough in diameter that the shoulder at the back of the pin is square. If it were radiused, much of the strain would be spread out...... but it ain't. Result: lots of broken firing pins from dry-firing and hardly any of the spares left.

Good luck with the toy. Toks are fun!
.
 
haretrigger said:
Just to update:
Sourced a used firing pin from Epps, and installed it - Not one fail to fire yet in 250 rounds of surplus!

What would cause a firing pin to crack? Dry firing? Excessive use?
Click to expand...

1 thing i do with the svt to avoid dry firing is to remove the rear cover(making sure the rifle is unloaded before) and holding the hammer down with a finger,then pull the trigger and slowly allow the hammer to rest against the bolt. Its a good way to keep the firing pin intact.
jocelyn
 
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